Motor-starting device



GI A.[BIIRNHAM.

MOTOR STARTING DEVICE.

APPLICATION FILED AUG.2, 1918.

1,415,521, Y PaIendMa-y 9,1922.

2 SHEETS-SHEET `l.

G. A. BURNHAM.

MOTOR STARTINGl DEVICE. APPLlcATloN HLED AuG.2.191a.

1,415,521 y Patented May 9, 1922.

2 SHEETS-SHEET 2.

UNITED STATES- P-ATENT OFFICE.

GEORGE A. BURNHAM, 0F SAUGUS, MASSACHSETTS, ASSIGNOR T SEARSlB. CONDIT,

JR., OF BROO'KLINE, MASSACHUSETTS.

MOTQR-STARTIN G DEVICE.

Specification of Letters Patent.

Patented May 9,1922.

, Application led August 2, 1918. Serial No. 247,975.

To all whom tmay concern.' l

Be it known that I, GEORGE A. BURNHAM, a citizen of the United States, residing in Saugus, in the county of Essex and State of Massachusetts, have invented an Improve ment in lVIotor-Starting- Devices, of which the following `is a specification.

My vinvention relates to induction motors, and has more particular reference tol means for starting induction motors.

In the operation of induction motors, and especially of the larger sizes, it is well known that it isy not advisable to connect 'said motors initially directly to the power circuit because of the excessive starting current taken fromthe system while they are being brought to normal speed; and it is therefore customary to employ starting or auto transformers, the auto-transformers being more commonly used. Said transformers are arranged to be initially connected between the line-or power circuit and the motor, ,and serve to reduce the voltage applied to the terminals of the motor, in theoperation of starting he motor, in order that. the current drawn from the line may be kept from rising to an abnormal value. A., double throw switch is customarily employed in connection with the starting transformer and motor, one side of which serves to connect the motor to the line or power circuit through the starting transformer, and the other side of 'which -serves to connect the motor directly to the line.

The starting transformer, considering particularly thefcasev of a three phase line,

has its coils permanently connected in Yv or V, and taps are extended from the ends of the coils for connection through the switch with the line'. Other taps are' brought out from intermediate points of the coils for connection through the switch with the motor, 'to provide a low voltage for the starting of the motor.

The double throw switch employed in connection with such a starting transformer has six' poles, which, with the transformer connections abovedescribed, is the minimum number of poles that can be employed and the switches must be of special construction.

The object of my invention is the provision of a system of connection between the' coils of the starting or auto-transformer, the motor and the starting' switch, whereby a single so-called standard type of switch commonly employed for various purposes,

coils, I prefer to extend leads from all ends of the coils to the switch, and transformer connections through the switch. I extend other leads from taps connected to intermediate points of the starting transformer coils to the motor, which leads are arranged to be permanent and 'in which no switch contacts are arranged.

lVith the arrangement above described, the double throw switch must be provided with three poles to provide for connections be tween the three wires composing the line, andthe transformer on one side, and the motor on the other, and one pole in addition, through which connection is made between the ends of the transformer coils, which is equivalent to the permanent junction heretofore always made between the coils in the auto-transformer.

A double throw four pole switch is therefore all that is necessary in order to adequately control the motor with the above described connections, and such a switch is a so-called standard type.

A much more compact combination of auto-transformer and switching equipment is possible by this arrangement of connection by which it is possible to employ a four pole switch, than bv the usual scheme of connection, which necessitated the use of a six pole double throw switch, and. for high voltage apparatus, permits a much greater spacing between poles of the switch and yet is more compact than is possible with the six pole switch and therefore provide for a greater margin of safety.

Fig.. represents the connections embed ing my invention, between a four pole double throw switch. a two coil auto-transformer and an induction motor adapted for connection to a three-phase line.

Fig. 2 represents the connections between a four pole double throw switch, a three coil auto-transformer and an induction motor adapted for connection with a three phase line.

F ig. 3 is a diagrammatic scheme of the complete the connections of Fig. 1, with the switch arranged for' the starting of the motor.

Fig. et is a diagrammatic scheme of connections of Fig. 1 with the switch arranged for the running of the motor.

Fig. 5 is a diagrammatic scheme of the connections of Fig. 2 with the switch arranged for the starting of the motor.

Fig. 6 is a diagrammatic scheme of the connections'of Fig. 2 with the switch arranged for the running of the motor.

Fig. 7 is a modified arrangement of the connections shown in Fig. 2.

Fig. 1 shows the scheme of connection between a four pole double t-hrow switch, an induction motor and a two coil auto-transformer or compensator arranged to control a motor, associated with a three phase line. The switch includes four starting switch members or brushes 10 and three running switch members or brushes 11. Said brushes 10 are connected together for conjoint movement and said brushes 11 are also connected together for conjoint movement as is well known. The switch is provided with four intermediate stationary members 12, 13, 14, and 15; a set of four stationarv contact members. 16, 17, 18 and 19 arranged on the starting side of the switch; and four station` ary contact members 20, 21, 22, and 23 arranged on the running side of the switch. The line wires 24C, 25, and 26 are arranged to be connected respectively with the intermediate stationary contact members 12, 13 and 14 of the switch.

The motor 27 is connected through leads to the stationary contact members 20, 21v

and 22 on the running side of the switch and is' adapted to be in permanent connection therewith. The starting transformer or compensator is provided with two coils 28 and 29, which have terminals 30 and 31 respectively extended from the coils and connected to the stationary switch members 1G and 17, arranged on the starting side of the switch. The other terminals 32 and 33 of the coils, instead of being permanently joined together, as has heretofore been universal practice are separately connected to switch members and the terminals 32 is con` nectcd with the .switch member 19 on thel starting side of the switch and the terminal 33 is connected to the intermediate starting switch member 1.5 ol the switch.

The junction or connection between the ends ol the coils is arranged to be made within the switch. as is hereinafter more fully described and it is by causing the connections between the ends of the coils heretofore permanently formed, to be under the control of the switch that a standard four pole switch may be employed.

The lead or jumper 34 is arranged to be connected on the outside ot the switch casing between the 'stationary switch member on running side of the switch and, through the leads or jumpers 35 and 34, serves to connect said brush with the stationary switch member 18 on the starting side ot' the switch; which connections are such that when the starting switch is closed, the ends 32 and 33 of the transformer coils .are connected together and to the line wire 2G. Although the flexible lead 36 is shown connected between said brush 10 and the switch member 23 on the running side ot' the switch, yet said brush may be connected in other ways with the switch members, as the purpose of such connections `is to connectvsaid brush and one of the linewires as 2G, when the switch is conditioned for starting. It is preferable, however, to extend the flexible lead 3G between said brush-10 and said member 23 in order that the switch may be adapted foruse either with a two coil compensator or with a three coil compensator, whereby the necessary slight alterations in connections may be made between the component parts of the switch extended beyond the switch enclosing casing.

The transformer coils, as is common, are provided with leads 37 and 38 which are eX- tended lrom intermediate points of said coils to provide a reduced voltage for the startingr of the motor and said leads are adapted to `be permanently joined to the motor leads.

lith the connections shown and described, it is evident that when the switch is moved into the' starting` position, the ends 3() and 31 of the transformer coils will be connected respectively to the line wires 25 and 24- and that the other ends 32 and 33 of said coils will be joined together within the switch casing by the brush 1() which bridges the stationary switch members 15 and 19 and that said junction will be connected through the flexible lead 36 and external jumpers 35 and 34 with 'the line wire 2G, thus completing the connection between the line and the transformer.

Due to the connections through the low voltage taps 37 and 33 between'the motor and compensator, a voltage less than the normal line voltage is impressed upon the terminals ot the motor, and the motor consequently begins to rotate. lVhen the motor has reached approximately its normal running speed. the switch may be nloved into the running position. ln this position the terminals 30 and 31 olI the transformer coils tion between the ends 32 and tion, the motor leads are'directly connected termediate to theline through the running switch members or brushes. The transformer, however, has potential applied to its coils through the permanent connection between the motor leads andthe low voltage taps 37 and 38 of the coils. This, however, is of no particular consequence because, as the coils .are openv ended, there can be no the coils, and therefore no loss of energy. Moreover, as the starting transformers or compensators are almost universally enclosed in the same casing with the starting switch, there are no exposed 'terminalsor leads which may be energized by' this scheme of connection other than the customary line and motor leads.

Fig. 2 illustrates the principle of the invention as applied to a three coil transformer. In this figure the construction of the four pole double throw switch is as before, and the motor 27 is connected as in Fig. 1, to the stationary switch members 20, 21 and 22 on the running side of the switch.

current flow through The starting transformer or compensator isprovided with three coils 40, 41 and 42, and ends or terminals 43, 44 and 45 are connected respectively to the stationary switch members -16, 7 and 18 on the starting side of the-switc nals 46, 47 and 48 of said coils, instead of being permanently connected or joined Itogether, as has heretofore universally been the case,` are extended and connected respectively to the stationary switch member 19 pn lthe starting side of the switch, the intermediate stationary switch member 15 and lthe stationary switch member 23 on the running side of the switch, which terminals are arranged to be joined together within the' switch casing when the switch is moved into starting position, in which position the brush 10, bridging the switch members .15 and 19, servesy to connect the terminals or ends 46 and 47 of the coils; and since said brush 1,0 is connected through the flexible lead 36 to the switch member 23,' it also serves to connect said terminals 46 and 47 with the terminalr48 of the coil.

, Taps 49, 50 and 51 are extended from inling position. the terminals 43, 44 and 45 of the three coil compensator are connected 'motor may thereby start to rotate.

The remaining-ends or termi- Y which condition the points of the coils of the transas 1s common practice` to provide for through the starting brushes 10 with the` line wires 24, 25 and 26, and the other ends 46, 47 and 48 of said coils are joined together within the switch casing, as has been previously explained thus forming, under the control of the switch,the standard form of connection between the transformer coils that has heretofore been made at the transformer.

The transformer coils are and a reduced the motor 27 Y taps 49, 50 and 51 of the coils, and tlxie s attained now energized voltage is impressed upon before, when the motor has substantially normal `running speed, the

switch is moved into the running position. The transformer terminals are thereby disconnected from the line through the separation of the starting switch members or brushes 1() from the starting switch members of the switch, and the junction between the other ends of said coils made within the switch casing is also broken; and the motor, through the running switch members 11. is directly connected to the line. Potential is applied to the transformer coils as before through the connection between the motor leads and theintermediate or low voltage taps vof the coil, but this, as before, is of little consequence, as it is to be understood that all connections between the starting transformer and switch made within the single enclosing casing and there are therefore no lead exposed to be energized, other than the usual line and motor leads,

The scheme of connections between the transformer coils and the\ double throw `switch is illustrated more clearly iny Figs. 3 to, 6 inclusive, which represent the connections between the coils and the line yin the starting and running conditions of the switch for a two former.

Fig. 3 shows the connection between the switch and the two coil transformer ar ranged for the starting .of the motor, in starting switch members or brushes 10 are closed, and the transformer coils are connected in open delta or `V to the line. The motor is shown as permanently connected through the taps 37 and 38 to the coils of the transformer. The running switch members or'brushes 11 are in open position and a low starting voltage may therefore be impressed upon the motor.

Fig'. 4 shows the switches and coils of the twov coil transformer, arranged for the Irunning of .the motor, in which case the' starting switch members or brushes 10 are in open position permanently coil and a three coil transthrough the intermediate arrangement of the and the running switch membersl or brushes 11 are in closed positionand the ends of and from the line.

4; isa-lapel Fig. 5 represents the scheme of connection with a three coil transformer in which the starting switch members or brushes l0 are closed, and the running switch members or brushes ll are open and the transformer is connected in Y for the starting of the motor.

lnFig. 6 the stationaryy switch members or brushes l0 are open and the coils are isolated from each other and from the line, and the running switch members or brushes ll are closed for the normal running of the motor.

The same principle is followed in vthe scheme of connections illustrating; both the two coil transformer and the three coil transformer., nstead et, as heretofore, connecting ends of the-transformer coils permanently together at the transformer to torni the desired open delta or Y connection, said ends of the coil are extended to the motor startingl switch and are adapted to be conneeted or joined together by the switch when the switch is operated tor the starting of the motorx d/hen the switch is thrown to the running side, the junction between the transformer coils is arranged 'to be broken thus destroying; the open delta or Y connec-m tion and, at the same time, the end s of the transformer coils which have been previously connectedto the line.l are now disn connected from it.. thus (le-energizing the transformer,

modiied arrangement of starting switch and. auto-transformer, incorporating the teatures of my inventions, is illustrated in Fig. 7 rlhis arrangement is quite similar to that shown in Fig. 2, inasmuch as a three coil transformer is employed. place of the standard four pole switch lshown in said Fig. 2, a standard three pole switch is here emloyed.

y yonnections between the switch, the transformer and the motor are made as before with the change that the ends or terminals 4-6, 47, and 48 of the three transformer coils are extended to three contact blocks 60, 6l

and 62 of a relay or contacter having a movable element 63 adapted to bridge and electrically connect said blocks upon the energization of its coil 64 to thereby connect the transformer coils in Y.

The energization of the coil. 64 of the contactor is controlled by an auxiliary switch 65 associated with the starting switch members, which may control the contactor circuit through one of the leads 66extending from a line wire 26 to the coil 64, the lead 6'? from the other end of the coil being directly connected to another line Wire, as 24.

ln operation, the switch 65 is., preferably, adapted to close before the main starting; switch members or brushes 10 and thereby the contacter is energized and has bridged and connected the contact blocks ,60. 6l and 62 before the main switch members have closed. With such an arrangement the contactor is not required to complete the circuit.

Upon opening the starting switch, or moving the switch from. the starting side tothe running side, said auxiliary switch 65 is designed to open after the starting' switch members or brushes 10 and therelorethe transformer circuit is already opened when the contacter is de-energized to disconnect the contact blocks and therefore the contactor does not interrupt the circuit.

By the early closing and delayed opening oit' the auxiliary switch .65, all the work ot interrupting the transformer circuit is performed by the starting switch members or brushes l0 which are designed for this purpose and the contacter doesno work and consequently the Contact members thereof may last indenitely.

rlbe auxiliary switch 65 is here shown diagrammatically and in practice a standard type of switch is employed which is adapted to be operated trom any convenient component ot the operating mechanism of the starting switch.

The contacter is also shown diagrammatically and it is obvious that its construction may be considerably modiied and the particular manner in which it operates to conneet or join the ends of the transformer to form the Y (or delta) scheme of connections may be also considerably modified and yet be within the scope of invention.

llith the arrangement of connections shown in Fig. 7, the sl-Lartingv switch. may be a standard tiree pole switch in place of the four pole switch required in tie connections shown in the previous igures, thus considerably reducing the cost of the starting switch, and the small auxiliary switch 65 may also be a standard switch.

1. Starting apparatus for three-phase induction motors comprising a starting tranvformer having normally open-ended coils, permanent connections between the motor and intermediate points of the transformer coils, a. double-throw switch having stationary switch members grouped into starting and running sets,v and a starting and a running set of movable brush members, said running set of brush members arranged to be actuated to connect the motor directly to a supply line for the running of the motor, and said starting set of movable brush members arranged to be actuated to connect the transformer to the supply line, and a pair of stationary switch members and a CoopersI ating brush'member arranged to be operated with said starting set of brush members to inter-connect the transformer coils and complete the circuit through the transformer for the starting of the motor.

2. A starting device for three-phase induction motors comprising a four-pole,

double-throw electric switch including a set of stationary switch members on the starting side of the switch, a second set of stationary switch members on the running side of the switch, a starting and a running set of movable brush members cooperating with said sets of stationary switch members, and a flexible jumper electrically connecting a brush member of the starting set of brush members with a stationary switch member of the running set of stationary switch members.

.3.- A starting devicevforthree-phase electric motors comprising a starting transformer having normally open ended coils, a four pole-double throw electric switch, and connections between said switch, transformer and the motor which admits of alternately connecting the motor through the transformer kto the line and interconnecting the. coils of the transformer, the motor directly to the line and breaking the connection between the coils of the transformer.

.4. A motor starting device comprising a. startin transformerv having a plurality of normally relatively unconnected coils, a switch to connect the motor directly to the line, a contactor to interconnect said coils, and means controlled by said lSwitch tov govern theoperatlon of the contactor.

5.' A motor startin device comprising a startin transformer norma 1y unconnected coils, a switch lto a1- ternately connect the motor direct-1y to the line, and through the transformer t0 the line, a contactor to interconnect the transformer coils, and an auxiliary switch controlled by aforesaid switch to govern the operation of the contactor.y

`starting transformer and connecting i aving a plurality of 6. Av motor starting device comprising a having three normally unconnected coils, a switch to alternately connect'the motor directly to the line, and through the transformer to the line, a contactor comprising threeecontact blocks each independently connected to an end of said transformer coils, a bridging member adapted to bridge and connect said contact blocks thereby to interconnect the coils of said transformer, and means controlled by said switch to'control the operation of said contactor. l

` 7. A motor starting device including a manually operable switch movable into a starting position for the starting of the motorand movable into a running position yfor the running of the motor, an auxiliary switch controlled bythe aforesaid switch, a-

motor-starting transformer having normally open-ended coils,

and an electrically controlled contactor controlled by said auxiliary switch to interconnect said normally opentrolled b Witnesses:

T. T. GREENWOOD, H. B. DAVIS.

a starting switch, and an 

